I'll ask what is the first logical thought :-)

Other than illegality, couldn't I just leave the 134a fittings and charge with r12 anyways?

Assuming I dedicate a 134 gauge set to r12 and I mark it.

I know you guys are going to say not to do this...but other than the legal aspect, why is it a bad idea?

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car